“Heretic, after the first and second admonitions, turn away” (Tit. 3.10)

“Heretic, after the first and second admonitions, turn away” (Tit. 3.10) The Holy Fathers of the Orthodox Church did not know such concepts as “Christian churches” or “heterodox denominations”. The heresy has always been called heresy, and its followers are called heretics.
The true Church of Christ is the Holy Orthodox Church, and all others who call themselves “Christian” are heretical communities. It is very sad that many words of God-bearing ascetics are now forgotten. - St. Anatoly of Optina